The present invention relates to the field of packaging articles, and in particular the field of packaging consumer products such as foods, chemicals, cosmetics, or pharmaceuticals, e.g. presented in the form of a receptacle having a closure device. More precisely, the invention relates to a security envelope for an article, particularly but not exclusively for a receptacle having a closure device, the envelope being of the type constituted by a sleeve of heat-shrink plastics material suitable for being fitted closely around a portion of the article.
Such security envelopes have been known for a long time, particularly in association with the necks of bottles, where they are intended to guarantee tamper-proofing for the consumer, by guaranteeing that the product concerned has not been subjected to fraudulent substitution or has not been maliciously tampered with. The security envelope is then conventionally in the form of a sleeve fitted with a tear strip, with the strip making it possible, by applying traction to one end thereof, to open the envelope in order to gain access to the closure device of the receptacle. Tampering is sometimes made more easily visible by having micro-perforations present in a particular pattern in the wall of the sleeve so that any attempt at forcibly pulling off the heat-shrunk envelope causes it to be torn and complicates putting it back into place on the receptacle.
Document GB-A-2 298 391 describes a security envelope of heat-shrink plastics material that is fitted on its inside face with a transferable hologram strip, and optionally with a tear strip disposed in the vicinity of and parallel to the hologram strip. The tear strip serves solely to provide the conventional function of making the envelope easier to tear, and does not contribute in any way to the security function which is provided by the hologram strip.
Document GB-A-2 273 492 describes the use of a hologram tear strip (i.e. the tear strip then itself carries the hologram) which is stuck to the inside face of a heat-shrink sleeve, with a line of perforations provided through both the strip and the wall of the sleeve. It should be observed that the free face of the strip is naturally not adhesive, so that when the sleeve is opened, the two separated portions of the strip remain associated with the walls of the sleeve.
Documents EP-A-0 585 076 and JP-A-08 022250 describe a technique very similar to the preceding technique, with a holographic strip stuck to the inside face of a heat-shrink sleeve. The free face of the strip is coated in a thickness of silicone (for roll packaging) so that the hologram is not transferable.
Proposals have also been made to make security envelopes in which the sleeve is fitted on its inside face with a holographic element and with a tear strip that passes behind the holographic element so as to tear said element when the envelope is opened by pulling on said strip.
Under such circumstances, the inside wall of the heat-shrink plastics material sleeve carries a holographic element made in the form of a patch and stuck directly to the inside wall of the sleeve, the patch having a layer of holographic metallization carried by a support layer of transparent plastics material adhering to the inside face of the sleeve. The zone affected by the tear strip is then in direct contact with the layer of holographic metallization. With such a security envelopes, when the user exerts traction on the end of the tear strip to open the envelope, the tear strip tears the side wall of the sleeve progressively and digs a gap in the holographic element when the separation zone reaches this element. Once the tear strip has been completely removed, the safety envelope can be opened, and the holographic element carried by said envelope is split into two segments each remaining on the inside wall of the envelope, on either side of the gap.
Such a holographic element is designed to constitute a certificate of origin for the product.
However, such a security envelope does not provide a genuine indication of tampering, particularly because the sleeve can be removed by sliding or cutting and then replaced by another envelope fitted on the inside with another holographic element that is identical or analogous to the original element. In some cases, the dishonest person can even unstick the original holographic element if it is very difficult to reproduce so as to stick it back on a new support which is then put back on the article.